Our biting spiders don't deserve a bad press

Auckland Museum's new exhibition The Poisoners is loaded with venomous plants and animals, some of which could be a toxic surprise lurking in your backyard, at the beach or in the bush - or even in your bathroom - this summer. In part two of this series on things that sting and bite, the experts look at spiders and sort fact from fiction.

The native katipo, like the redback, can give a nasty bite but is so shy that few people are bitten. Photo / Supplied
The native katipo, like the redback, can give a nasty bite but is so shy that few people are bitten. Photo / Supplied

Tales of necrotic flesh and paralysis after a bite have given spiders a bad press but most local arachnids pose little threat to humans.

Auckland Museum entomology curator John Early says there are two spiders that fall outside that category - the katipo and the redback spider.

"Both have a distinctive orange or red stripe on their back but while the katipo or 'night stinger' is a native, its relative the redback is an import from our Australian neighbours.

"In the top half of the North Island katipo spiders have lost their red stripe and are pure jet black with a satiny sheen, but they are still just as dangerous.

"They typically inhabit the sandy dunes around our shorelines so it's possible you could stumble across them on your summer holiday but population decline and their shy, retiring nature means katipo are not a common sight.

"Redbacks prefer to live inland around buildings and debris on the farm and section. They are restricted to a few regions, like parts of Central Otago."

Dr Early says bites from katipo and redbacks aren't common because the spiders are reclusive and not aggressive by nature.

"They're not looking for confrontation but if they feel threatened and you're in their space, then they're more likely to bite."

A bite from a katipo or redback can cause intense abdominal, back or chest pain in addition to pain at the site.

Other symptoms include nausea, vomiting, headaches and hypertension, and in the case of a bite people are advised to head to a hospital for observation and assistance and, in some cases, antivenom.

"The venom is slow to spread in the body and take full effect so you have time to get medical help.

"Don't compress the bite, suck or scratch it. Keep it clean and apply ice in a plastic bag to help ease the pain and prevent swelling."

Another spider that has made headlines in recent years is the white tailed spider - also from Australia - which has a long, thin, dark grey body with a white tip.

Dr Early says research has so far ruled out links between these spiders and tissue necrosis (tissue cells rapidly dying off) but because the bite creates a puncture wound there is a risk of secondary infection.

"It's that secondary infection, if the wound gets something in it or is not kept clean, that is most likely responsible for the dramatic stories about white tail bites, but the chances are it's not even a white tail bite in the first place.

"White tails are just as likely to be found inside as outside.

"Parents looking to motivate their offspring to clean up after themselves may like to point out that among the white tailed spider's popular hangouts are clothes or items left on the floor. The more hiding places the better."

Dr Early says New Zealanders can count themselves lucky the country is free of aggressive species like the Sydney funnel-web spider which delivers venom that is deadly to humans and often strikes repeatedly in an attack.

Poison plan

* Spiders can inject neurotoxic venom via their bite.

* Pain and swelling at the site are usually the principal outcome for a spider bite in New Zealand but it can also lead to intense abdominal, back or chest pain, nausea, vomiting, headaches and hypertension.

* In the event of a bite, try to stay still, place a cold pack on the bite to relieve pain but do not apply pressure. Seek medical assistance - head to hospital if there is one in the area.

* If you can do so safely, take the offending spider with you so it can be identified and you can get the right antivenom if necessary.

* In the event of poisoning, advice can be sought from the New Zealand National Poisons Centre on 0800 POISON (0800 764 766) - this toll-free service operates 24 hours a day.

- NZ Herald

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